Introduce malloc_last_fail() which returns the number of seconds since

malloc(9) failed last time.  This is intended to help code adjust
memory usage to the current circumstances.

A typical use could be:
	if (malloc_last_fail() < 60)
		reduce_cache_by_one();

1 files changed, 16 insertions, 0 deletions

diff --git a/sys/kern/kern_malloc.c b/sys/kern/kern_malloc.c
index 3d6307a..577b5da 100644
--- a/sys/kern/kern_malloc.c
+++ b/sys/kern/kern_malloc.c
@@ -46,6 +46,7 @@
 #include <sys/vmmeter.h>
 #include <sys/proc.h>
 #include <sys/sysctl.h>
+#include <sys/time.h>
 
 #include <vm/vm.h>
 #include <vm/pmap.h>
@@ -134,6 +135,16 @@ static int sysctl_kern_mprof(SYSCTL_HANDLER_ARGS);
 
 static int sysctl_kern_malloc(SYSCTL_HANDLER_ARGS);
 
+/* time_uptime of last malloc(9) failure */
+static time_t t_malloc_fail;
+
+int
+malloc_last_fail(void)
+{
+
+	return (time_uptime - t_malloc_fail);
+}
+
 /*
  *	malloc:
  *
@@ -191,6 +202,11 @@ out:
 		ksp->ks_maxused = ksp->ks_memuse;
 
 	mtx_unlock(&ksp->ks_mtx);
+	if (!(flags & M_NOWAIT))
+		KASSERT(va != NULL, ("malloc(M_WAITOK) returned NULL"));
+	if (va == NULL) {
+		t_malloc_fail = time_uptime;
+	}
 	return ((void *) va);
 }